When did you sail on Costa and which ship- maybe things have changed! It seems like we had very different cruises- and we are experienced travellers (cruises and land vacations- always 5 star on land) There were basically NO announcements so if you think they were constant , things must have changed! The staff was excellent all around with the exception of our butler. In fact, they seemed more genuine than the staff we dealt with on Celebrity. Re: noise- at times I thought the ship was TOO QUIET- not enough going on some of the time. And coming back to food- I do not think any of the mass market cruise lines deliver true 5 star restaurant dining (perhaps Radisson, Seabourn etc are exceptions to this) but in MY experience there was little difference that I could see between Celebrity, Costa, RCCL, and NCL. Each of them did some things very well to excellently and each could have improved on some things but overall none stand out as significantly better or worse than others and our Costa experience was very good (and we DO eat regularly in 5 star restaurants).
We also thought our suite was the best designed and most spacious of all our experiences and that the ship just seemd to be less crowded than we have experienced in the past- we could always find a deck chair at any time of the day.
Anyway that is our experience- I have no vested interest in extolling the virtues of Costa- just telling it like we saw it so people can get a balanced picture!